Oak Ridge Rail Bridge

Pratt Pony Truss Bridge over Big Sioux River
Near Rock Valley, Sioux County, Iowa
Hudson, Lincoln County, South Dakota

Click the Photo Above to See All Photos of This Bridge!
Name Oak Ridge Rail Bridge
Built By Chicago, Milwaukee St. Paul & Pacific Railway
Contractor Lassig Bridge & Iron Works of Chicago
Currently Owned By D&I Railroad
Length 805 Feet Total, 125 Foot Main Span
Width 1 Track
Height Above Ground 15 Feet (Estimated)
Superstructure Type Pratt Pony Truss, Deck Girder and Trestle
Substructure Type Timber and Steel Pile
Date Originally Built Ca. 1899
Date Relocated 1914
Original Location Iowa Division?
Traffic Count 2 Trains/Day (Estimated)
Current Status In Use
D&I Bridge Number T-598
Significance Moderate Significance
Documentation Date December 2014
In 1878, the Sioux City & Pembina Railway built a line from Elk Point, South Dakota to Sioux Falls, South Dakota.

The line crossed across the Big Sioux a number of times, crossing between Iowa and South Dakota.

The line was merged into the Sioux City and Dakota Railroad in 1879.

By 1881, the line became a branch of the Chicago, Milwaukee & St. Paul Railway, also known as the Milwaukee Road.

In 1913, following an escapade to the Pacific Ocean, the railroad became known as the Chicago, Milwaukee St. Paul & Pacific Railway.

Heading north out of Sioux Falls, the Milwaukee Road also operated a branch to North Dakota.

By 1981, with the Milwaukee Road falling to bankruptcy, the Dakota & Iowa (D&I) Railroad was formed as a joint coalition between Iowa and South Dakota to operate the former branch to Sioux City.

Today, D&I continues to operate the line from Sioux Falls to Sioux City, as well as the Dell Rapids branch.

Another unique bridge crossing the Big Sioux River on this route is this structure, near the ghost town of Oak Ridge.
Originally built in approximately 1899, this bridge features a 6-panel pin connected Pratt Pony Truss. This span was likely built along the Council Bluffs-Green Island route through central Iowa.
Evidence of this is the relocation date of 1914. Between 1912 and 1914, the entire Iowa Division mainline was completely rebuilt. Trusses like this were exceedingly common along the route, before being replaced.
In addition to the main truss span, there is a single deck girder span to the south of the bridge. Pile trestle spans also approach the bridge.
However, these trestle spans were extensively rebuilt in 2014 after a large flood damaged the structure.

The author has ranked this bridge as being moderately significant, due to the relocation history.
The photo above is an overview.

Big Sioux River Railroad Bridges
Upstream Fairview Rail Bridge
Downstream DAIR Hudson Rail Bridge


Source Type


Build Date Milwaukee Road Archives at the Milwaukee Central Library
Railroad Line History Source ICC Valuation Information, Compiled by Richard S. Steele

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